The following keywords are used to help with the Pixel Joint search tool and to help search engines with appropriate key phrases. Make sure to take some time and add keywords to your pixel art submissions. It actually helps!
X4 - ZX Aile avatars, X4 - ZX Aile icons, X4 - ZX Aile pixel art, X4 - ZX Aile forum avatars, X4 - ZX Aile AOL Buddy Icons
Shading, proportions and colouring are in X4 style. The design however is a ZX one, designed in the style of ZX art. Which makes it clash with anything within X4 as a natural result. Non bulky humanoid Reploids and humans don't make an appearence in the game and thus have no sprites to compare to. As a result, it's probably more accurately a pseudo X4 style.
Coincidentally, the ZX art style's influencing of designs is also the reason why her appearence is childlike and lacking in female shapes.